| FUSARIUM CANKERS,
Several species of
Fusarium are known to cause cankers in black walnut in the Midwest and North
Carolina. Trees in other States are also probably affected by the canker.
Elongate cankers of various lengths
usually occur on the lower portions of the main stems of young trees, near the
ground line. However, cankers may also occur higher on the stem or on branches
in the lower crown of young trees. Cankers first appear as breaks in the bark
or as expanding sunken areas. Darkly stained, diseased wood can be found
beneath the bark. An affected tree often produces sprouts near the canker or at
the base of the stem. Sometimes tiny pinholes caused by an ambrosia beetle can
be found within the cankered area.
Affected trees show
cankered, stained areas on the stems. An otherwise normal-looking tree that is
producing many basal sprouts is commonly cankered. The primary injuries caused
are wilting of leaves and dieback of the top. When the top has died, a sprout
may take over and replace the lost tree, but several years of growth are
Cut and remove
diseased trees from the plantation. Prune dormant trees and burn or remove
pruning debris from the area.